Stick-slip is a phenomenon in which a shaft seal’s sealing lip and the shaft surface alternate between adhesion and slipperiness. This alternating sticking and slipping is caused by insufficient lubrication. This insufficiency may be due to lack of proper initial lubrication, or it could be that high underlip temperatures have thinned the lubricant to the point that it can no longer consistently support the radial load of the seal.

Applications with splash lubrication at the seal area are prone to have stick-slip problems with the seal. As illustrated in Figure 252, axial tears (known as chatter marks) in the seal contact pattern are indicative of stick-slip. Stick-slip often allows leakage and may, in extreme cases, even destroy the seal.

The key to preventing stick-slip is to make sure the sealing lip stays well lubricated. You might opt for a design with two lips, making sure that the area between the lips is grease-packed.

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